MicroRNAs (miRs) have emerged as promising biomarkers for early disease diagnosis and personalised treatment monitoring. However, but their clinical utility has been hampered by technical limitations. Dynamic chemical labelling (DCL) based on capturing abasic PNA probes and reactive nucleobases, so-called SMART bases, is a PCR-free approach that has proven very useful for the direct interrogation of circulating miRs. In this work, we expand the palette of available tools for DCL miR detection methods with a newly synthesised SMART nucleobase, SMART-C-Eu. This nucleobase contains a stable lanthanide cryptate. Using this SMART-C-Eu base and time-gated (TG) luminescence imaging, we successfully detect and quantify miR-122-5p in human serum sam...